1. Field of the Invention
The present invention generally relates to a resistive force sensing circuit for sensing physically-applied inputs and a resistive force sensing apparatus thereof.
2. Description of the Related Art
Currently, touch sensing has been successfully applied in many fields, such as portable device input, medical monitor and electronic point of sale (POS) system. Touch control mechanisms include: resistive, capacitive, optical, etc. Resistive sensing has an advantage in its ability to combine touch and force sensing through force-sensing resistor (FSR). Although early resistive touch control technique can only detect one touch point, various solutions can offer multi-touch or force-sensing points recently.
However, in many cases, when an input device with a simple FSR matrix circuit contains multi-point force-sensing function, the output value can be affected by the number of input pressure points and force levels. That is, even the user applies the same force on one point of the device, the output value of the point can change depending on how the rest of the sensing surface is touched. This may cause “ghost point” phenomenon, when the system output a touch point at a location not touched. Furthermore, the input device with a simple FSR array or matrix circuit may have high leakage currents between each input point or part, which may interfere with the output values and consume more power.
Although there have been many solutions to overcome the problems described above, such solutions usually utilize extra components such as op-amps, or complex algorithms. Therefore, the costs of production and maintenance of such solutions inevitably become higher, in addition to increased chance of malfunction